1. Field of the Invention
This invention relates to electrical connectors and more particularly to a connector for leadless integrated circuit packages.
2. Description of the Prior Art
The need for an improved integrated circuit packaging system has become critical, from a profit standpoint, with companies that are trying to use highly developed electronic technology in commercial and consumer applications such as automotive, appliances, communication, industrial components, industrial systems, and the like.
The need stems from the inability of the otherwise excellent dual-in-line package (DIP) to physically meet manufacturing, testing, assembly, and servicing requirements that are being imposed thereon. This problem is due to the leads of the DIP not being strong enough for the manual and mechanical handling that they are receiving as they are being employed in a variety of new products.
This problem with the leads of integrated circuit packages, along with the desire to reduce costs, has led to the development of leadless integrated circuit packages of both the dual-in-line type and what has become known as the 2 .times. 2 substrate. In place of leads, these leadless packages employ terminal pads located adjacent the edges of a flat ceramic substrate, and the terminal pads are connected to discrete solid state circuits mounted on the substrate. The dual-in-line leadless package is usually rectangular and the terminal pads are located adjacent the opposite longitudinal edges. The 2 .times. 2 substrate is square and is usually provided with terminal pads adjacent each of its peripheral edges. Specific positioning of the terminal pads is accomplished in three ways which are referred to as: face mount, side mount, and edge mount. The face mount technique places the terminal pads on one face, or planar surface, of the substrate with the pads disposed adjacent to at least two edges. The side mount technique locates the terminal pads on two opposite edges of the substrate so that the pads are disposed in planes which are perpendicular to the planar surfaces of the substrate. The edge mount technique is similar to the commonly employed method used in printed circuit boards in that the pads are located on both planar surfaces of the substrate and are located adjacent the same one edge thereof.
Commercial acceptance of these leadless packages has been relatively slow due to various problems such as connectors for mounting and electrically interconnecting the packages with a backpanel such as a printed circuit board or wiring panel.
Various connector configurations have been employed or suggested for the various leadless connectors, with these prior art connectors being relatively bulky and multipart complex structures. Since the use of terminal pads dictates that a pressure type of interconnection be employed, the forces needed to achieve reliable connections becomes quite large and can become a serious problem when relatively large numbers of interconnections are to be made.
One particular prior art connector employs a base which is mounted on the backpanel by soldering or otherwise attaching the wire wrap pins, which depend from the base, into the backpanel. The leadless package is mounted within a recess provided in the base and the terminal pads of the package are pressurized into conductive contact with upwardly extending portions of the wire wrap pins. The necessary downward pressurization is accomplished by means of a cover hingedly mounted on the base. This, and similar prior art connectors are usually employed only on relatively small leadless packages of the type having terminal pads on only two edges thereof due to the inability of such covers to achieve equal pressurization over long spans and on packages having terminal pads on more than two edges.
Another type of prior art connector employs a base, similar to the one described above, for receiving the leadless package. A force exerting element is placed on the leadless package and is pressurized downwardly by means of a cover which is screwed in place. The screws are located only at the corners or ends of such connectors, as determined by the geometric configuration, so as not to sacrifice valuable contact space. Such a mounting technique complicates servicing and when relatively large leadless packages are mounted in this type of connector, uneven contact pressurization can result in the spans between the mounting screws due to deflection or bowing of the cover and the force exerting element.
A particular prior art connector, which is fully disclosed in U.S. Pat. No. 3,904,262, issued on Sept. 9, 1975, to the same inventor, includes a base receptacle mounted on a backpanel and having contact means therein which are in contact with the backpanel. The receptacle is adapted to receive the circuit package therein so that the terminal pads thereof are in alignment with the contact means provided in the receptacle. A cover is removably mounted in the receptacle and is laterally slidable relative thereto into and out of engagement with inclined plane members formed in the receptacle. When the cover is moved into engagement with the inclined plane members it will be deflected downwardly and locked in place to load the terminal pads of the circuit package into conductive contact with the contact means of the base receptacle. This connector, while constituting a substantial improvement in the art has some drawbacks, in that the wedging action provided by engagement of the cover with the inclined plane members is exerted only on three sides of the circuit package thus making it possible for unequal pressurization of the terminal pads on the fourth side of the circuit package to occur. Further, this prior art connector requires the usage of tooling to accomplish the required lateral sliding of the cover thereof.
In view of the foregoing, the need exists for a new and improved connector for leadless integrated circuit packages which overcomes some of the problems of the prior art.